Both retaining walls and freestanding walls are frequently constructed from concrete blocks. For increased stability, the blocks may be formed with interlocking knobs and grooves between blocks in adjacent tiers of blocks to prevent movement of the tiers of blocks.
A wall may be constructed around a building as a force containment wall, to reduce damage to the building from an explosion outside the wall. The containment wall also can prevent vehicles from entering a secure region around a building. For example, such a wall may be constructed, to prevent the possibility of a terrorist vehicle containing a bomb from approaching a government building. In this situation, the strength of the wall is important if the wall is to successfully prevent breach of the secure area by a determined vehicle driver.
Strong, one-piece walls may be formed from concrete poured in place and reinforced with steel rods. However, these walls are expensive and take longer to construct than a wall formed from precast blocks stacked into tiers. Additionally, poured concrete walls cannot be moved after they are constructed. On the other hand, a wall which is formed from stacked concrete blocks can be quickly constructed and later moved. However, such a wall may not provide the security of a one-piece wall and may be more easily breached by a vehicle or by an explosion.